Tube clamping die



June 28, 1955 F. R. WILSON 2,711,772

TUBE CLAMPING DIE Filed Sept. 9, 1953 I lllL-Jllll I INVENTOR. v pl oFRANK R. WILSON BY DES JARDINS, ROBINSON 8. KEISER HIS ATTORNEYS atentOfl ice Patented June 28, 1955 TUBE CLAMPING DIE Frank R. Wilson,Memphis, Tenn.

Application September 9, 1953, Serial No. 379,253

5 Claims. (Cl. 153-79) This invention relates to tube clamping dies foruse with tube flaring tools, and more particularly, to an improvement inthose types of clamping dies in which the clamping recesses are providedwith chamfers at their upper edges to back up the flare on the tube asit is formed by the flaring cone.

It has heretofore been the practice in the construction of tube clampingdies for use with flaring cones of conventional design to provide achamfer on the upper edge of each clamping recess to back up the flareon the tube as the flaring cone is forced into the end of the tubethereby facilitating the accurate shaping of the flare produced by thecone. In the past, it has been customary to make the taper of thechamfer correspond with the taper on the flaring cone, that is, in toolshaving a 45 flaring cone, the recesses of the clamping dies are providedwith 45 chamfers. As a result, when the flaring cone is forced into theend of a tube held in the clamping die, a sharp corner is formed at thebottom of the flare where it joins the tube. A weakness is therebyintroduced into the flared tube at the point where the flare joins thetube and cracking or splitting of the tube at this point is likely tooccur, and complete separation or breaking off of the flare may result.

For the purpose of eliminating this source of weakness in the tube, 1have found that it is helpful to make the angle of inclination of thechamfer from 5 to 10 less than that of the cone so that when the cone isforced into the tube, a clearance or relief will be provided at thebottom of the chamfer provided excessive axial force is not appliedtothe cone. The formation of a sharp corner at the bottom of the flarewill thereby be avoided since the corner formed by the intersection ofthe chamfer with the walls of the recess will not be forced into thewall of the tube at this point.

In order to more positively insure that no indentation of the tube willoccur at the point where the flare joins the cylindrical portion of thetube and to cause a transition fillet portion to be formed between thecylindrical portion of the tube and the wall of the flare formedthereon, the bottom portion of the chamfer may be removed to provide aclearance or relief extending circumferentially around the base of thechamfer so as to prevent contact between the wall of the tube and thedie. As hereinafter to be described, this relief may be pro- .vided bycounterboring the upper end of the cylindrical portion of the recess soas to remove the corner formed by the intersection of the chamfer withthe cylindrical portion of the recess. The diameter of the counterboreneed be only slightly greater than the diameter of the clamping recessin order to provide the necessary clearance. By thus relieving thebottom of the chamfer, positive assurance is given that the sharp,bottom edge of the chamfer will not form a sharp corner at the bottom ofthe flare formed on the end of the tube. The corner formed by theintersection of the top of the counterbore with the bottom of thechamfer is preferably rounded to avoid indenting the tube at thislocation and, to the same end, the angle of inclination of the chamfermay be made less than that of the cone to relieve the pressure on thetube at the bottom of the chamfer. Also, to prevent any indenting of thewall of the flare by the corner formed at the intersection of thechamfer with the top face of the clamping die, this corner may berounded slightly to prevent nicking or indenting of the flare at thispoint.

Accordingly, it is an object of my invention to so modify the shape andinclination of the chamfered surface as to prevent sharp corners orindentations being formed in the flared portion of the tube. Experiencehas shown that such sharp corners or indentations introdece a weaknessin the tube and render it subject to splitting or cracking at this pointwhile the tube is in service.

Another object of my invention is to provide a chamfer on the upper edgeof the die opening which is inclined at a substantially steeper anglethan the sides of the flaring cone so as to cause the location ofmaximum pressure of the cone on the tube to occur at the top of thechamfer.

Another object of my invention is to provide a counterbore in the lowerpart of the chamfer, which is of larger diameter than the clampingrecess, so that the corner formed by the intersection of the chamfer andthe recess is relieved and the formation of a sharp corner at the bottomof the flare is avoided.

Another object of my invention is to round the corner formed by theintersection of the chamfer with the top face of the die, and also toround the corner at the top of the counterbore to prevent annulargrooves or indentations being formed in the outer surface of the flareat these locations. t

With these and other objects in view which will become apparent from thefollowing description, the invention includes certain novel features ofconstruction and combinations of elements, the essential features ofwhich are set forth in the appended claims and a preferred form orembodiment of which will hereinafter be described with reference to thedrawings which accompany and form a part of this specification.

In the drawings:

Fig. 1 is a side view of a tube flaring tool incorporating my invention.

Fig. 2 is a fragmentary view illustrating a conventional type ofclamping die.

Fig. 3 is a fragmentary view illustrating a clamping die incorporatingthe teachings of my invention.

Fig. 4 is a fragmentary view of a clamping die incorporating stillfurther teachings of my invention.

In Fig. 1 of the drawings there is shown a tube flaring tool having aflaring cone and advancing means therefor of conventional design. Thetube to be flared, shown in phantom outline in Fig. 1 and indicated byreference numeral it), is held in a clamping die, indicated generally at11, which is secured on the lower ends of the legs of a yoke 12. Thisdie may be of the same general type as that shown and described in U. S.Patent No. 2,563,088, patented August 7, 1951, on an application filedby Karl W. Wilks, In, and Glenn W. Wolcott. That is, the clamp ing diemay consist of two complementary die blocks 1, the second block lyingdirectly behind the one shown in this figure. Each block is providedabout its periphery with a plurality of semi-cylindrical clampingrecesses of different diameters for receiving the different sizes oftubes to be flared. At its upper end, each recess 15 is provided with achamfer 16 which provides a back-up surface for the tube when the coneis forced therein during the tube flaring operations.

The neck of the yoke 12 is provided in the usual man ner with a threadedhole for receiving a threaded advancing spindle 2%). On the lower end ofthe spindle is mounted a flaring cone 21 of conventional design which isadapted to be forced into the end of the tube 10 held in the clampingdie 11 when the spindle is rotated by means of a handle 22 secured onthe upper end of the spindle. As the pointed end of the cone 21 isforced downwardly into the open end of the tube It), the sidewalls ofthe tube will be spread outwardly at an angle corresponding to the angleof inclination of the sides of the cone as shown in Fig. 2.

The clamping die construction shown in Fig. 2 follows the teachings ofthe prior art in which a die block 25, formed with a semicylindricalclamping recess 26 for receiving a tube 27 to be flared, is provided atits upper end with a chamfer 28 the inclination of which is the same asthat of the flaring cone 29. Accordingly, when the end of the tube isflared outwardly by the cone 29 being forced therein, as indicated inFig. 2, a sharp corner will be produced where the bottom of the flarejoins the cylindrical portion of the tube 27. This is due to the sharpcorner 30, formed by the intersection of the bottom of the chamfer withthe cylindrical wall of the clamping recess 26 being forced into thewall of the tube. Likewise, if excessive pressure is applied to theflaring cone, an annular indentation will be formed in the outside wallof the flare by the sharp corner 31 formed by the intersection of theupper edge of the chamfer 28 with the top face of the clamping block.The tube will be greatly weakened at these points, particularly at thepoint where the bottom of the flare joins the cylindrical portion of thetube 27. The life of 35 is formed with a semicylindrical clamping recess36 for receiving a tube 37 to be flared. At the upper end of the recess36 is a chamfer 38 which, as clearly shown in Fig. 3, is pitched at asteeper angle than the walls of the cone 39. Consequently, when the coneis forced into the end of the tube, the point of maximum pressuralcontact of the outer wall of the flare against the surface of theclamping block will be at the upper end of the chamfer where itintersects with the top face of the clamping block. Also, the cornerformed by the bottom of the chamfer with the cylindrical wall of therecess 36, which corner is indicated by reference numeral 4-0 in Fig. 3,will now he below the point of bend in the tube 37. Hence, the flaredtube will be formed with a small fillet, or curve of small radius, asindicated by reference numeral 41, at the point where the flare joinsthe tube. The creation of a sharp corner at this critical location onthe tube will thereby be avoided.

With a 45 cone, the angle of the chamfer 38 (Fig. 3) is preferably inthe neighborhood of 35 to 40 so as to afford ample clearance between thebottom of the flare and'the lower portion of the chamfer. To avoid anypossibility of the formation of an annular indentation in the outsidewall of the flare at the upper end of the chamfer,

the corner formed by the intersection of the chamfer with the top faceof the die may be rounded as indicated by reference numeral 42.

Another form of my invention is shown in Fig. 4 wherein the constructionillustrated in Fig. l is shown on a much larger scale. As illustratedherein, the chamfer 16, like the chamfer 38 (Fig. 3), is pitched at asteeper angle than the sides of the cone 21, though to a lesser degreeas hereinafter specified, so as to provide relief in the die at thebottom of the chamfer as explained earlier herein, i. e., to relieve thepressure on the tube at the bottom of the chamfer. However, to provideroom for the tube 10 to bend at the point where the bottom of the flareconnects with the cylindrical portion of the tube so as to provide atransition fillet portion between the cylindrical wall portion of thetube being flared and the conical wall portion of the flare, indicatedby reference numeral in Fig. 4, the upper end of the recess 15 iscounterbored as indicated at 46 thereby providing additional relief inthe vicinity of the bottom of the chamfer. This counterbore ispreferably of a cylindrical character and is of only slightly greaterdiameter than the clamping recess 15. The effect of the counterbore isto remove the bottom portion of the chamfer 16, the portion removedpreferably being in the neighborhood of from 10 to 40%. The depth of thecounterbore, that is the point at which the counterbore steps, which isindicated by reference numeral 47 in Fig. 4, is not critical but has thefunction of determining the radius of curvature of the fillet at thebottom of the flare. That is, the greater the depth of the counterbore,the larger the radius of the fillet since the transition fillet portionwill be coextensive with the relief provided in the die. In theconstruction shown in Fig. 4, the angle of inclination of the chamfer 16is preferably in the neighborhood of 40 to 43, i. e., 2 to 5 less thanthat of the cone, and the corner at the top of the counterbore isrounded as indicated by reference numeral 49. Also, the corner at thetop of the chamfer is rounded as indicated by reference numeral 48 inthe same manner and for the same purpose as described earlier herein inconnection with the embodiment shown in Fig. 3.

While I have described my invention in connection with a particular formof embodiment thereof and, have used, therefore, certain specificillustrations and descriptions thereof, it is to be understood that thepresent disclosure is illustrative rather than restrictive and thatchanges and modifications may be resorted to without departing from thespirit or scope of the claims which follow.

Having thus described my invention, what I claim as new and useful, anddesire to secure by United States Letters Patent, is:

1. A tube clamping device for use with a tube flaring tool having aflaring cone comprising a pair of separable dies each having one or moresemicylindrical recesses formed therein, the recesses in one of saiddies being complementary to the recesses in the other of said dies, achamfer on the upper edge of each recess for supporting the outer faceof the flare as it is formed on the end of the tube, and means forproviding a transition fillet portion between the cylindrical wallportion of the tube being flared and the conical wall portion of theflare, said means including a relieved die wall surface extendingcircumferentially around the base of each chamfer and restricted to thetransition fillet portion of the tube so as to prevent contact of theouter face of said transition fillet portion of the tube with therelieved die wall surface resulting from the application of a normalaxial force to said flaring cone during the flaring or burnishingoperation.

and the tube wall to occur at the top edge of the chamfer.

References Cited in the file of this patent UNITED STATES PATENTS TimkenDec. 30, 1919 Davies Feb. 10, 1931 Bratz Jan. 7, 1941 Wilks Aug. 7, 1951OTHER REFERENCES Pages 157, 158 and 159 of a book entitled Press-Working of Metals by Oberlin Smith, copyrighted in 1896 by John Wileyand Sons, a copy of which may be found in Div. 14, and having librarymarking of TS-253-.S6.

